US President-elect Donald Trump announced Monday that his son-in-law Jared Kushner, a property developer and publisher, will serve as senior White House advisor, flouting myriad legal and ethical concerns.

The incoming Republican, who has never previously held elected office, said Kushner, who also has no political experience outside his father-in-law's campaign, would serve as "senior advisor to the president."

Kushner, whom Forbes estimates is worth $1.8 billion together with his parents and adult brother, will forego his salary while serving in the administration, said a statement from the transition team.

The 35-year-old will work closely with White House chief of staff Reince Priebus and chief strategist Steve Bannon to execute Trump's agenda, it added.

"Jared has been a tremendous asset and trusted advisor throughout the campaign and transition and I am proud to have him in a key leadership role in my administration," Trump announced.

"He has been incredibly successful, in both business and now politics. He will be an invaluable member of my team as I set and execute an ambitious agenda, putting the American people first," he added.

Priebus called Kushner "a visionary with a rare ability to communicate with and assemble broad coalitions of support" and said his "open mind, adaptability and keen intellect" would be a "great asset" to the team.

Kushner welcomed the appointment as "an honor" and said he was "humbled" by the opportunity to serve.